Created Adding Multi-region Support (markdown)

Adding-Multi-region-Support.md

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+When making a hack, you may want the player to visit more than one region and with how Pokémon Emerald is set up, there is no way of identifying the region.
+
+This tutorial will walk you through how to add the support for multiple regions through the available mapsection IDs. How to do this is simple.
+
+Firstly, we need to open **[src/overworld.c](https://github.com/pret/pokeemerald/blob/master/src/overworld.c)** as there are two functions we need to change.
+
+Find `LoadCurrentMapData` and make the following change:
+```diff
+static void LoadCurrentMapData(void)
+{
+    sLastMapSectionId = gMapHeader.regionMapSectionId;
+    gMapHeader = *Overworld_GetMapHeaderByGroupAndId(gSaveBlock1Ptr->location.mapGroup, gSaveBlock1Ptr->location.mapNum);
+    gSaveBlock1Ptr->mapLayoutId = gMapHeader.mapLayoutId;
+    gMapHeader.mapLayout = GetMapLayout();
++    gMapHeader.region = sMapsecToRegion[gMapHeader.regionMapSectionId];
+}
+```
+This function handles the loading of the data for the currently loaded map 
+Right below that function, there is `LoadSaveblockMapHeader`, which handles loading the respective map data on save resume. We need to make the following change:
+```diff
+static void LoadSaveblockMapHeader(void)
+{
+    gMapHeader = *Overworld_GetMapHeaderByGroupAndId(gSaveBlock1Ptr->location.mapGroup, gSaveBlock1Ptr->location.mapNum);
+    gMapHeader.mapLayout = GetMapLayout();
++    gMapHeader.region = sMapsecToRegion[gMapHeader.regionMapSectionId];
+}
+```
+If you notice, we've add `gMapHeader.region` which loads data in `sMapsecToRegion` which we will be covering.
+
+Next, we need to open **[include/global.fieldmap.h](https://github.com/pret/pokeemerald/blob/master/include/global.fieldmap.h)** and find the struct `MapHeader` which should look like this:
+```c
+struct MapHeader
+{
+    /* 0x00 */ const struct MapLayout *mapLayout;
+    /* 0x04 */ const struct MapEvents *events;
+    /* 0x08 */ const u8 *mapScripts;
+    /* 0x0C */ const struct MapConnections *connections;
+    /* 0x10 */ u16 music;
+    /* 0x12 */ u16 mapLayoutId;
+    /* 0x14 */ u8 regionMapSectionId;
+    /* 0x15 */ u8 cave;
+    /* 0x16 */ u8 weather;
+    /* 0x17 */ u8 mapType;
+    /* 0x18 */ u8 filler_18[2];
+    /* 0x1A */ u8 flags;
+    /* 0x1B */ u8 battleType;
+};
+```
+`u8 filler_18[2]` is our point of interest here as it's simply used for padding the struct by two bytes. We will be using one of those bytes for our own `region` byte, like so:
+```diff
+struct MapHeader
+{
+    /* 0x00 */ const struct MapLayout *mapLayout;
+    /* 0x04 */ const struct MapEvents *events;
+    /* 0x08 */ const u8 *mapScripts;
+    /* 0x0C */ const struct MapConnections *connections;
+    /* 0x10 */ u16 music;
+    /* 0x12 */ u16 mapLayoutId;
+    /* 0x14 */ u8 regionMapSectionId;
+    /* 0x15 */ u8 cave;
+    /* 0x16 */ u8 weather;
+    /* 0x17 */ u8 mapType;
+-    /* 0x18 */ u8 filler_18[2];
++    /* 0x18 */ u8 filler_18;
++    /* 0x19 */ u8 region;
+    /* 0x1A */ u8 flags;
+    /* 0x1B */ u8 battleType;
+};
+```
+Now, we are going to be adding a new array that will be used for our new region field.
+For the sake of this tutorial, we will be using Hoenn, Kanto and the Sevii Islands.
+Open **[include/overworld.h](https://github.com/pret/pokeemerald/blob/master/include/overworld.h)** and add the following:
+```diff
++enum {
++    REGION_HOENN,
++    REGION_KANTO,
++    REGION_SEVII
++};
+```
+These are IDs for the different regions with `REGION_HOENN` being 0, `REGION_KANTO` being 1 and `REGION_SEVII` being 2.
+We are now going to add the array.
+I prefer to put this into its own file, but you need to have the following somewhere in **[src/overworld.c](https://github.com/pret/pokeemerald/blob/master/src/overworld.c)**:
+```diff
++static const u8 sMapsecToRegion[] = {
++    [MAPSEC_LITTLEROOT_TOWN]            = REGION_HOENN,
++    [MAPSEC_OLDALE_TOWN]                = REGION_HOENN,
++    [MAPSEC_DEWFORD_TOWN]               = REGION_HOENN,
++    [MAPSEC_LAVARIDGE_TOWN]             = REGION_HOENN,
++    [MAPSEC_FALLARBOR_TOWN]             = REGION_HOENN,
++    [MAPSEC_VERDANTURF_TOWN]            = REGION_HOENN,
++    [MAPSEC_PACIFIDLOG_TOWN]            = REGION_HOENN,
++    [MAPSEC_PETALBURG_CITY]             = REGION_HOENN,
++    [MAPSEC_SLATEPORT_CITY]             = REGION_HOENN,
++    [MAPSEC_MAUVILLE_CITY]              = REGION_HOENN,
++    [MAPSEC_RUSTBORO_CITY]              = REGION_HOENN,
++    [MAPSEC_FORTREE_CITY]               = REGION_HOENN,
++    [MAPSEC_LILYCOVE_CITY]              = REGION_HOENN,
++    [MAPSEC_MOSSDEEP_CITY]              = REGION_HOENN,
++    [MAPSEC_SOOTOPOLIS_CITY]            = REGION_HOENN,
++    [MAPSEC_EVER_GRANDE_CITY]           = REGION_HOENN,
++    [MAPSEC_ROUTE_101]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_102]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_103]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_104]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_105]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_106]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_107]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_108]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_109]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_110]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_111]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_112]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_113]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_114]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_115]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_116]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_117]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_118]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_119]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_120]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_121]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_122]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_123]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_124]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_125]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_126]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_127]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_128]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_129]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_130]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_131]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_132]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_133]                  = REGION_HOENN,
++    [MAPSEC_ROUTE_134]                  = REGION_HOENN,
++    [MAPSEC_UNDERWATER_124]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_126]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_127]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_128]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_SOOTOPOLIS]      = REGION_HOENN,
++    [MAPSEC_GRANITE_CAVE]               = REGION_HOENN,
++    [MAPSEC_MT_CHIMNEY]                 = REGION_HOENN,
++    [MAPSEC_SAFARI_ZONE]                = REGION_HOENN,
++    [MAPSEC_BATTLE_FRONTIER]            = REGION_HOENN,
++    [MAPSEC_PETALBURG_WOODS]            = REGION_HOENN,
++    [MAPSEC_RUSTURF_TUNNEL]             = REGION_HOENN,
++    [MAPSEC_ABANDONED_SHIP]             = REGION_HOENN,
++    [MAPSEC_NEW_MAUVILLE]               = REGION_HOENN,
++    [MAPSEC_METEOR_FALLS]               = REGION_HOENN,
++    [MAPSEC_METEOR_FALLS2]              = REGION_HOENN,
++    [MAPSEC_MT_PYRE]                    = REGION_HOENN,
++    [MAPSEC_AQUA_HIDEOUT_OLD]           = REGION_HOENN,
++    [MAPSEC_SHOAL_CAVE]                 = REGION_HOENN,
++    [MAPSEC_SEAFLOOR_CAVERN]            = REGION_HOENN,
++    [MAPSEC_UNDERWATER_SEAFLOOR_CAVERN] = REGION_HOENN,
++    [MAPSEC_VICTORY_ROAD]               = REGION_HOENN,
++    [MAPSEC_MIRAGE_ISLAND]              = REGION_HOENN,
++    [MAPSEC_CAVE_OF_ORIGIN]             = REGION_HOENN,
++    [MAPSEC_SOUTHERN_ISLAND]            = REGION_HOENN,
++    [MAPSEC_FIERY_PATH]                 = REGION_HOENN,
++    [MAPSEC_FIERY_PATH2]                = REGION_HOENN,
++    [MAPSEC_JAGGED_PASS]                = REGION_HOENN,
++    [MAPSEC_JAGGED_PASS2]               = REGION_HOENN,
++    [MAPSEC_SEALED_CHAMBER]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_SEALED_CHAMBER]  = REGION_HOENN,
++    [MAPSEC_SCORCHED_SLAB]              = REGION_HOENN,
++    [MAPSEC_ISLAND_CAVE]                = REGION_HOENN,
++    [MAPSEC_DESERT_RUINS]               = REGION_HOENN,
++    [MAPSEC_ANCIENT_TOMB]               = REGION_HOENN,
++    [MAPSEC_INSIDE_OF_TRUCK]            = REGION_HOENN,
++    [MAPSEC_SKY_PILLAR]                 = REGION_HOENN,
++    [MAPSEC_SECRET_BASE]                = REGION_HOENN,
++    [MAPSEC_DYNAMIC]                    = REGION_HOENN,
++    [MAPSEC_PALLET_TOWN]                = REGION_KANTO,
++    [MAPSEC_VIRIDIAN_CITY]              = REGION_KANTO,
++    [MAPSEC_PEWTER_CITY]                = REGION_KANTO,
++    [MAPSEC_CERULEAN_CITY]              = REGION_KANTO,
++    [MAPSEC_LAVENDER_TOWN]              = REGION_KANTO,
++    [MAPSEC_VERMILION_CITY]             = REGION_KANTO,
++    [MAPSEC_CELADON_CITY]               = REGION_KANTO,
++    [MAPSEC_FUCHSIA_CITY]               = REGION_KANTO,
++    [MAPSEC_CINNABAR_ISLAND]            = REGION_KANTO,
++    [MAPSEC_INDIGO_PLATEAU]             = REGION_KANTO,
++    [MAPSEC_SAFFRON_CITY]               = REGION_KANTO,
++    [MAPSEC_ROUTE_4_FLYDUP]             = REGION_KANTO,
++    [MAPSEC_ROUTE_10_FLYDUP]            = REGION_KANTO,
++    [MAPSEC_ROUTE_1]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_2]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_3]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_4]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_5]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_6]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_7]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_8]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_9]                    = REGION_KANTO,
++    [MAPSEC_ROUTE_10]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_11]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_12]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_13]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_14]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_15]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_16]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_17]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_18]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_19]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_20]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_21]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_22]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_23]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_24]                   = REGION_KANTO,
++    [MAPSEC_ROUTE_25]                   = REGION_KANTO,
++    [MAPSEC_VIRIDIAN_FOREST]            = REGION_KANTO,
++    [MAPSEC_MT_MOON]                    = REGION_KANTO,
++    [MAPSEC_S_S_ANNE]                   = REGION_KANTO,
++    [MAPSEC_UNDERGROUND_PATH]           = REGION_KANTO,
++    [MAPSEC_UNDERGROUND_PATH_2]         = REGION_KANTO,
++    [MAPSEC_DIGLETTS_CAVE]              = REGION_KANTO,
++    [MAPSEC_KANTO_VICTORY_ROAD]         = REGION_KANTO,
++    [MAPSEC_ROCKET_HIDEOUT]             = REGION_KANTO,
++    [MAPSEC_SILPH_CO]                   = REGION_KANTO,
++    [MAPSEC_POKEMON_MANSION]            = REGION_KANTO,
++    [MAPSEC_KANTO_SAFARI_ZONE]          = REGION_KANTO,
++    [MAPSEC_POKEMON_LEAGUE]             = REGION_KANTO,
++    [MAPSEC_ROCK_TUNNEL]                = REGION_KANTO,
++    [MAPSEC_SEAFOAM_ISLANDS]            = REGION_KANTO,
++    [MAPSEC_POKEMON_TOWER]              = REGION_KANTO,
++    [MAPSEC_CERULEAN_CAVE]              = REGION_KANTO,
++    [MAPSEC_POWER_PLANT]                = REGION_KANTO,
++    [MAPSEC_ONE_ISLAND]                 = REGION_SEVII,
++    [MAPSEC_TWO_ISLAND]                 = REGION_SEVII,
++    [MAPSEC_THREE_ISLAND]               = REGION_SEVII,
++    [MAPSEC_FOUR_ISLAND]                = REGION_SEVII,
++    [MAPSEC_FIVE_ISLAND]                = REGION_SEVII,
++    [MAPSEC_SEVEN_ISLAND]               = REGION_SEVII,
++    [MAPSEC_SIX_ISLAND]                 = REGION_SEVII,
++    [MAPSEC_KINDLE_ROAD]                = REGION_SEVII,
++    [MAPSEC_TREASURE_BEACH]             = REGION_SEVII,
++    [MAPSEC_CAPE_BRINK]                 = REGION_SEVII,
++    [MAPSEC_BOND_BRIDGE]                = REGION_SEVII,
++    [MAPSEC_THREE_ISLE_PORT]            = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_6]               = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_7]               = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_8]               = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_9]               = REGION_SEVII,
++    [MAPSEC_RESORT_GORGEOUS]            = REGION_SEVII,
++    [MAPSEC_WATER_LABYRINTH]            = REGION_SEVII,
++    [MAPSEC_FIVE_ISLE_MEADOW]           = REGION_SEVII,
++    [MAPSEC_MEMORIAL_PILLAR]            = REGION_SEVII,
++    [MAPSEC_OUTCAST_ISLAND]             = REGION_SEVII,
++    [MAPSEC_GREEN_PATH]                 = REGION_SEVII,
++    [MAPSEC_WATER_PATH]                 = REGION_SEVII,
++    [MAPSEC_RUIN_VALLEY]                = REGION_SEVII,
++    [MAPSEC_TRAINER_TOWER]              = REGION_SEVII,
++    [MAPSEC_CANYON_ENTRANCE]            = REGION_SEVII,
++    [MAPSEC_SEVAULT_CANYON]             = REGION_SEVII,
++    [MAPSEC_TANOBY_RUINS]               = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_22]              = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_23]              = REGION_SEVII,
++    [MAPSEC_SEVII_ISLE_24]              = REGION_SEVII,
++    [MAPSEC_NAVEL_ROCK_FRLG]            = REGION_SEVII,
++    [MAPSEC_MT_EMBER]                   = REGION_SEVII,
++    [MAPSEC_BERRY_FOREST]               = REGION_SEVII,
++    [MAPSEC_ICEFALL_CAVE]               = REGION_SEVII,
++    [MAPSEC_ROCKET_WAREHOUSE]           = REGION_SEVII,
++    [MAPSEC_TRAINER_TOWER_2]            = REGION_SEVII,
++    [MAPSEC_DOTTED_HOLE]                = REGION_SEVII,
++    [MAPSEC_LOST_CAVE]                  = REGION_SEVII,
++    [MAPSEC_PATTERN_BUSH]               = REGION_SEVII,
++    [MAPSEC_ALTERING_CAVE_FRLG]         = REGION_SEVII,
++    [MAPSEC_TANOBY_CHAMBERS]            = REGION_SEVII,
++    [MAPSEC_THREE_ISLE_PATH]            = REGION_SEVII,
++    [MAPSEC_TANOBY_KEY]                 = REGION_SEVII,
++    [MAPSEC_BIRTH_ISLAND_FRLG]          = REGION_SEVII,
++    [MAPSEC_MONEAN_CHAMBER]             = REGION_SEVII,
++    [MAPSEC_LIPTOO_CHAMBER]             = REGION_SEVII,
++    [MAPSEC_WEEPTH_CHAMBER]             = REGION_SEVII,
++    [MAPSEC_DILFORD_CHAMBER]            = REGION_SEVII,
++    [MAPSEC_SCUFIB_CHAMBER]             = REGION_SEVII,
++    [MAPSEC_RIXY_CHAMBER]               = REGION_SEVII,
++    [MAPSEC_VIAPOIS_CHAMBER]            = REGION_SEVII,
++    [MAPSEC_EMBER_SPA]                  = REGION_SEVII,
++    [MAPSEC_SPECIAL_AREA]               = REGION_KANTO,
++    [MAPSEC_AQUA_HIDEOUT]               = REGION_HOENN,
++    [MAPSEC_MAGMA_HIDEOUT]              = REGION_HOENN,
++    [MAPSEC_MIRAGE_TOWER]               = REGION_HOENN,
++    [MAPSEC_BIRTH_ISLAND]               = REGION_SEVII,
++    [MAPSEC_FARAWAY_ISLAND]             = REGION_HOENN,
++    [MAPSEC_ARTISAN_CAVE]               = REGION_HOENN,
++    [MAPSEC_MARINE_CAVE]                = REGION_HOENN,
++    [MAPSEC_UNDERWATER_MARINE_CAVE]     = REGION_HOENN,
++    [MAPSEC_TERRA_CAVE]                 = REGION_HOENN,
++    [MAPSEC_UNDERWATER_105]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_125]             = REGION_HOENN,
++    [MAPSEC_UNDERWATER_129]             = REGION_HOENN,
++    [MAPSEC_DESERT_UNDERPASS]           = REGION_HOENN,
++    [MAPSEC_ALTERING_CAVE]              = REGION_HOENN,
++    [MAPSEC_NAVEL_ROCK]                 = REGION_SEVII,
++    [MAPSEC_TRAINER_HILL]               = REGION_HOENN
++};
+```
+Don't forget to declare it somewhere in **[src/overworld.c](https://github.com/pret/pokeemerald/blob/master/src/overworld.c)** like so:
+```diff
++static const u8 sMapsecToRegion[];
+```
+If I explained this correctly and didn't miss anything out, you should be able to compile the changes using `make` and the game will now use the region field for the current map the player is on.
+With this, you can do things like add battle music that changes depending on the region the player is in. I will update this tutorial at some point with how you can do this.